Stereoacuity and Aniseikonia: Evaluation Before and After Bilateral Implantation of Three Types of Presbyopia-Correcting Intraocular Lenses in Uncomplicated Phacoemulsification with Due Consideration of Interocular Differences in Higher Order Aberrations, Axial Lengths, Refractive Errors, and Acuities.

PURPOSE

To determine if the changes in stereoacuity and aniseikonia, following bilateral implantation of presbyopia correcting intraocular lenses could be predicted from preoperative measurements of higher order aberrations (HOAs), axial lengths (AL), refractive errors (RE) and corrected visual acuities (CVAs).

PATIENTS AND METHODS

Stereoacuity (Randot tests, @6m & 40cm, in steps of 20 arcsecs") vertical and horizontal aniseikonia (Awaya test @6m, in steps of 1%) with best correction and HOAs (Shack-Hartmann aberrometer) were measured before, 3 and 6 months after uncomplicated bilateral phacoemulsification. Twenty patients (I) underwent a mix-and-match procedure (Tecnis MF, ZKB00 in one eye and ZLB00 in the other), 17 (II) were implanted with a trifocal (AT LISA 839 triMP) and 18 (III) with a one-piece diffractive (Synergy OU) intraocular lens. The resultant aniseikonia (A) of vertical and horizontal pairs of aniseikonia measurements was calculated using the Pythagorean theorem. Twenty untreated age/gender matched cases were recruited as controls (IV).

RESULTS

The key results (p < 0.001) were a) stereoacuity at distance (SAD) and near (SAN) improved, A reduced in groups I, II & III remaining unchanged in group IV; b) some significant intergroup differences in SAD, SAN & A were detected at postop; c) at 6 months postop, changes (Δ=pre- minus postoperative value) correlated with preoperative values (x). Linear regression revealed, I ΔSAD=0.66x-57.47 [0.832, ±66.4], ΔSAN=0.96x-34.59 [0.821, ±16.9], ΔA=0.93A-2.12 [0.795, ±1.4] II ΔSAD=0.79x-62.91 [0.916, ±38.1], ΔSAN=0.96x-31.49 [0.892, ±8.0], ΔA=0.91A-0.91 [0.839, ±1.3] III ΔSAD=0.67x-35.50 [0.991, ±23.7], ΔSAN=0.88x-38.51[0.988, ±10.6], ΔA=0.86A-0.96 [0.900, ±1.3]. Figures in parentheses are the corresponding and ±limits of agreement between actual and estimated values. Definitive overarching associations connecting interocular differences in HOAs, AL, RE, and CVAs with SAD, SAN and A were not found.

CONCLUSION

Changes in stereoacuity and aniseikonia can be predicted using preoperative values. ΔSAN can be predicted within ±1, and ΔA within ±2, scale divisions. In group III ΔSAD can be predicted within ±1, and in group I ±3, scale divisions.